Good day all. I was almost decided on Canon 70-300 USM IS (non L) but recently came to know about the Tamron version (SP AF 70-300 F/4-5.6 Di VC USD) of this one. Neither of these makes you a better photographer and the price is neck to neck as well. The Tamron version features a non rotating front element and full time manual focusing. Its VC is also slightly better reviewed than Canon IS. Sharpness is almost same. Color quality wise Tamron wins by margin, though it has CS issues. Tamron one is heavier and build quality is better.
I've found a few links which you can take a look.
Canon 70-300mm USM IS:
Tamron 70-300mm USD VC:
Review and Sample Photos:
Side by Side Comparison:
If you were given a 550D body and 500$ to buy a lens, which one of the above would you've bought?
And about type of photography I want to do, I was thinking birds mostly, but also anything good thats far enough! =) Auto focus is also reviewed as faster in Tamron considering the time it takes to focus from MFD to Infinity. Focus is acurate and with the help of FTM, you can fine tune as well. (after all its their anniversary lens!). Its slightly sharper than Canon beyond 200mm but also slightly softer than Canon below 200.
I dont know much about sharpness of other lenses (I do not own any L series lens) or what you guys call sharp, but you can take a look at this full size bird photos and let me know if they are sharp or not.
All photos taken using a Canon EOS 50D with the Tamron 70-300 attached, Aperture Priority mode, handheld with the VC system On. More pictures taken by Tamron 70-300 can be found in Here (flickr).